Distance-based hybrid automatic repeat request (harq) location unavailable configuration for group sidelink communication

ABSTRACT

A transmitting user equipment (UE) device sends a location unavailable configuration to a receiving UE device indicating whether hybrid automatic repeat request (HARQ) messages should be sent by the receiving UE device for distance-based HARQ when location information is unavailable to the receiving UE device. The receiving UE device is one of a group of UE devices receiving a groupcast data transmission from the transmitting UE device where the groupcast data transmission comprises a distance-based HARQ feedback configuration. After detecting that HARQ feedback should be provided, the receiving UE determines that location information is unavailable. The HARQ feedback is provided in accordance with the location unavailable configuration. A HARQ message is transmitted where the location unavailable configuration requires transmission of HARQ when location information is

CLAIM OF PRIORITY

The present application claims the benefit of priority to Provisional Application No. 63/028,348 entitled “Groupcast Sidelink HARQ Feedback With No Location Information”, docket number TPRO 00349 US, filed May 21, 2020, assigned to the assignee hereof and hereby expressly incorporated by reference in its entirety.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to patent application entitled “HYBRID AUTOMATIC REPEAT REQUEST (HARQ) FEEDBACK MANAGEMENT BASED ON LOCATION INFORMATION AVAILABILITY FOR GROUP SIDELINK COMMUNICATION”, docket number TUTL 00349A PC, and patent application entitled “HYBRID AUTOMATIC REPEAT REQUEST (HARQ) FEEDBACK MANAGEMENT BASED ON LOCATION INFORMATION AVAILABILITY AND SIDELINK SIGNAL QUALITY FOR GROUP SIDELINK COMMUNICATION”, docket number TUTL 00349C PC, both filed concurrently with this application and incorporated by reference in their entirety herein.

FIELD

This invention generally relates to wireless communications and more particularly to distance-based hybrid automatic repeat request (HARQ) location unavailable configuration for group sidelink communication

BACKGROUND

Many wireless communication systems that employ several base stations that provide wireless service to user equipment (UE) devices enable sidelink communication between two or more UE devices where the UE devices can communicate directly with other UE devices. Such sidelink communications sometimes include one UE device (group leader UE device) that transmits the same data to multiple UE devices in a group. Different transmission techniques often referred to as cast types can be used to transmit the same data to multiple UE devices. Cast types include at least unicast, groupcast and broadcast. A unicast transmission can only be received by the single UE device that is the intended recipient of the data. Accordingly, multiple transmissions are required to send the same data to multiple UE devices using unicast. A broadcast transmission can typically be received by all UE devices within range of the transmission. A groupcast transmission can only be received by the UE devices that are members of a group. Accordingly, for example, the group leader UE device can transmit the same data in a single transmission using groupcast to two or more UE devices in the group or can send the same data in multiple unicast transmissions to the UE devices.

SUMMARY

A transmitting user equipment (UE) device sends a location unavailable configuration to a receiving UE device indicating whether hybrid automatic repeat request (HARQ) messages should be sent by the receiving UE device for distance-based HARQ when location information is unavailable to the receiving UE device. The receiving UE device is one of a group of UE devices receiving a groupcast data transmission from the transmitting UE device where the groupcast data transmission comprises a distance-based HARQ feedback configuration. After detecting that HARQ feedback should be provided, the receiving UE determines that location information is unavailable. The HARQ feedback is provided in accordance with the location unavailable configuration. A HARQ message is transmitted where the location unavailable configuration requires transmission of HARQ when location information is unavailable. The receiving UE refrains from transmitting a HARQ message where the location unavailable configuration requires no transmission of HARQ when location information is unavailable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of a communication system including a first user equipment (UE) device, a second UE device, a third UE device, a fourth UE device, and two base stations.

FIG. 2 is a block diagram of an example of a communication device suitable for use as each of the base stations.

FIG. 3 is a block diagram of an example of a UE device suitable for use as each of the UE devices.

FIG. 4 is a message flow diagram for an example where a transmitting UE device provides a location unavailable configuration to a receiving UE device.

FIG. 5 is a flow chart of an example of a method of managing groupcast feedback based on location information availability.

FIG. 6 is a flow chart of an example of a method of managing groupcast feedback based on location information availability.

DETAILED DESCRIPTION

As discussed above, different cast types can be used for communication between UE devices. Although UE device groups may be formed and used in different situations and environments, one scenario where grouping UE devices is particularly useful includes vehicle platoons where vehicles dynamically form a platoon while traveling together. All the vehicles in the platoon obtain information from the leading vehicle to manage the platoon. In some implementations, the information facilitates travel of the vehicles in the same direction in a coordinated manner and allows the vehicles to drive closer than in normal situations where there is no communication between the vehicles. Vehicles of the same platoon are involved in sharing the necessary information required to support the platoon operations where the information may include, for example, the distance between vehicles, relative speeds, and updates from roadside units (RSUs). Similar requirements also apply to the Extended Sensor use case where UE devices exchange data gathered through local sensors or live video data among vehicles, RSUs, pedestrian devices, and V2X application servers. Groupcast techniques allow efficient transmission of the information from one UE device, such as the platoon leader, to the other UE device members of the group.

In accordance with revisions of 3GPP communication specifications, sidelink communications between a transmitting UE device and receiving UE device(s) are managed with feedback messaging. In order to achieve reliable communications, for example, both unicast and groupcast communications support hybrid automatic repeat request (HARQ) feedback over sidelink in order for the transmitting UE device to determine if retransmissions are needed and if the modulation code scheme (MCS) needs to be relaxed to provide a more robust retransmission to reach the receiving peer UE device. With unicast transmissions, HARQ feedback for both acknowledgement (ACK) and negative acknowledgement (NACK) are supported and addressed to a single peer UE device. With groupcast transmissions, however, the transmitting UE device configures HARQ feedback which may include ACK/NACK feedback or only NACK feedback. The transmitting UE device of the groupcast transmission my receive HARQ feedback from multiple peer UE devices on the Physical Sidelink Feedback Channel (PSFCH). In order to save HARQ feedback resources on the PSFCH, the feedback for groupcast may be configured by the transmitting UE device for two general configurations. For a first configuration, the receiving UE device transmits HARQ-NACK on PSFCH if it fails to decode the corresponding transport block (TB) after decoding the associated PSCCH. With the first configuration, the receiving UE device transmits no signal on PSFCH otherwise. With a second configuration, the receiving UE device transmits HARQ-ACK on PSFCH if it successfully decodes the corresponding TB and it transmits HARQ-NACK on PSFCH if it does not successfully decode the corresponding TB after decoding the associated PSCCH targeting the receiving UE device.

More specifically, when the transmitting UE device transmits data to group member receiving UE devices, the packet consists of both the traffic data and the header including Sidelink Control Info (SCI). The SCI is encoded with a more robust modulation coding scheme (MCS) than the data so that the receiving UE devices will more easily receive this portion of the signal. The traffic portion of the packet is encoded with a relatively less robust MCS to ensure higher data throughput. Therefore, if the receiving UE device only successfully receives the control signal portion (SCI) without successfully receiving the data portion, the receiving UE device sends a “NACK” to the transmitting UE device. For the option where both ACK and NACK are required for feedback, the receiving UE device is required to send ACK when the data portion is received successfully. When the receiving UE device cannot decode the SCI the receiving UE device does not send either ACK nor NACK. Such a situation corresponds to the HARQ DTX case where the transmitting UE device determines that the receiving UE device did not receive the packet if no feedback is received within a HARQ feedback timer.

In addition, the transmitting UE device may enable distance-based HARQ feedback. With distance-based HARQ feedback, the receiving UE device sends HARQ feedback only if the receiving UE device is within a configured communication range away from the transmitting UE device. Typically, distance-based HARQ requires NACK only feedback. For conventional systems, the transmitting UE device indicates its current Zone ID and a communication range requirement in the Sidelink Control Info (SCI). The receiving UE device calculates the distance from the current location of the receiving UE device to the center of that particular Zone ID indicated in the SCI received from the transmitting UE device. If the distance is less than the communication range requirement, the receiving UE device sends the NACK for HARQ feedback. Therefore, when distance-based HARQ is configured, the receiving UE devices that are far away from the transmitting UE device do not send HARQ feedback. Such a configuration not only reduces the use of PSFCH resources, but it prevents the transmitting UE device from making unnecessary retransmissions where a NACK is received since the retransmission will likely not be successfully received by those far away receiving UE devices.

In some situations, location information is not available to a UE device. Typically, such a situation is temporary rather than an issue with the capability of the UE device. In most situations where the transmitting UE device does not have its own location information, the transmitting UE device will not configure distance-based HARQ feedback of the receiving UE devices of the group.

An issue arises when the transmitting UE device has location information and configures distance-based HARQ feedback for groupcast transmissions, but location information is unavailable to one or more of the receiving UE devices. In this case, the receiving UE device cannot determine if it is within communication range and whether HARQ feedback should be sent.

One possible mechanism to address this problem is to require any receiving UE device that does not have location information to refrain from sending HARQ feedback if distance-based HARQ feedback is configured. Such a technique has the benefit that PSFCH resources can be saved for other UE devices and useless retransmissions may be avoided. In some situations, however, the receiving UE device may be well within the communication range but HARQ feedback cannot be sent. An example of such a situation occurs when the receiving UE device passes through a coverage hole. As a result, the service performance may be unnecessarily severely degraded by restricting HARQ feedback even though the receiving UE device is within communication range of the transmitting UE device.

Another possible way to address the problem is to require that receiving UE devices to always send HARQ even when they do not have location information and distance-based HARQ feedback is configured. Such a technique is of course beneficial from the preserving the QoS, especially for high priority service. The technique, however, may result in increased use of PSFCH resources and unnecessary retransmissions, especially where the receiving UE devices are outside the communication range and the data portion of the retransmissions is not likely to be received successfully. Such situations could render the HARQ feedback system unusable.

Therefore, distance-based HARQ feedback management is needed for efficient transmission of HARQ feedback when location information is unavailable to a receiving UE device. For the distance-based HARQ feedback management techniques discussed herein, the transmitting UE device configures the receiving UE device to either transmit HARQ messages or refrain from transmitting HARQ messages when location information is unavailable to the receiving UE device. For the examples herein, the transmitting device sends a location unavailable configuration to the receiving UE devices to configure the receiving UE devices. In one example, the transmitting UE device determines whether HARQ should be sent when location information is unavailable. In another examples, the base station and/or network makes the determination. In some situations, the determination is be made collaboratively by the transmitting UE device and the base station and/or the network.

FIG. 1 is a block diagram of an example of a communication system 100 including a first user equipment (UE) device 101, a second UE device 102, a third UE device 103, a fourth UE device 104, and two base stations 106, 108. Although the techniques discussed herein may be applied to various types of systems and communication specifications, the devices of the example operate in accordance with at least one revision of a 3GPP New Radio (NR) V2X communication specification. The techniques discussed herein, therefore, may be adopted by one or more future revisions of communication specifications although the techniques may be applied to other communication specifications where sidelink or D2D is employed. More specifically the techniques may be applied to current and future releases of 3GPP NR specifications. For example, the techniques may also be applied to 3GPP NR (Rel-17). For the example, the UE devices 101-104 may be any type of device that can receive signals from, and transmit signals to, base stations and other UE devices. The UE devices operate in the communication system that includes a plurality of base stations that each provide wireless service within a service area. For the example of FIG. 1 , the first UE device 101 is served by a first base station 106 and the other UE device 102-104 are served by either the first base station 106 or a second base station 108 and may transition between base stations in accordance with known handover techniques. Each of the UE devices 101-104, therefore, may be served by a different base station even though two or more UE devices are communicating with each other using a sidelink connection.

For the example, the first UE device 101 is a transmitting UE device and the other UE devices 102-104 are receiving UE devices and are members of a group. The group data for the group may be transmitted in groupcast transmissions from the transmitting UE device 101. In some situations, the group data may be transmitted over a unicast communication link to a member of the group. For the example, a groupcast transmission 110 including groupcast data is transmitted from the first UE device (transmitting UE device) 101 to the second UE device 102 and the third UE device 103. The group data is also sent over a unicast communication link to the fourth UE device 104. The first UE device 101, therefore, may also be referred to as the transmitting UE device and source UE device, herein. Although the example includes three UE devices 102, 103, 104 in the group, the group may include any number of devices.

For the example of FIG. 1 , the fourth UE device 104 receives the group data in a unicast transmission 111 over unicast communication link and therefore provides HARQ feedback in accordance with the unicast connection. The second UE device 102 and the third UE device 103 are sent the group data over a groupcast data transmission specifying a distance-based HARQ feedback. For the example, the third UE device 103 is in a situation where distance based HARQ is invoked. More specifically, location information is available to the third UE device 103, the third UE device determines it is within the specified communication range, and the third UE device is unable to successfully receive the data portion of the groupcast data transmission 110. As a result, the third UE device 103 transmits a distance-based HARQ NACK message 114 in accordance with the distance-based HARQ configuration established by the transmitting UE device 101. The HARQ messages 112, 114 are transmitted over the PSFCH in accordance with known techniques.

The second UE device 102, however, does not successfully receive the data portion of the groupcast data transmission but does not have location information for the example. With conventional systems, there is no established technique for dealing with such a situation. For the examples herein, however, the transmitting UE device 101 provides a location-unavailable configuration 116 to the receiving UE devices indicating how a receiving UE device should handle distance-based HARQ feedback when location information is not unavailable to the receiving UE device. After receiving the SCI in the groupcast data transmission 110 and determining that the data portion could not be successfully received, the second UE device 102 determines whether a HARQ message should be transmitted based on the location-unavailable configuration 116. If the location-unavailable configuration 116 indicates HARQ feedback should be provided when location information is unavailable, the second UE device 102 transmits a HARQ message 118. Otherwise, no HARQ message is transmitted. The arrow representing the HARQ message is FIG. 1 is shown a dashed line to indicate that the HARQ message 118 is transmitted in accordance with the location-unavailable configuration 116 and, therefore, is not transmitted in some circumstances. For the examples herein, if the receiving UE device does not receive the location-unavailable configuration or if the location-unavailable configuration is not sent, the second UE device 102 transmits a HARQ message 118. In other situations, the default can be set such that no HARQ message is sent where the location-unavailable configuration is not sent.

FIG. 2 is a block diagram of an example of a base station 200 suitable for use as each of the base stations 106, 108. The base station 200 includes a controller 204, transmitter 206, and receiver 208, as well as other electronics, hardware, and code. The base station 200 is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to the base stations 102, 104 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices. The base station 200 may be a fixed device or apparatus that is installed at a particular location at the time of system deployment. Examples of such equipment include fixed base stations or fixed transceiver stations. Although the base station may be referred to by different terms, the base station is typically referred to as a gNodeB or gNB when operating in accordance with one or more communication specifications of the 3GPP V2X operation. In some situations, the base station 200 may be mobile equipment that is temporarily installed at a particular location. Some examples of such equipment include mobile transceiver stations that may include power generating equipment such as electric generators, solar panels, and/or batteries. Larger and heavier versions of such equipment may be transported by trailer. In still other situations, the base station 200 may be a portable device that is not fixed to any particular location.

The controller 204 includes any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of the base station 200. An example of a suitable controller 204 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 206 includes electronics configured to transmit wireless signals. In some situations, the transmitter 206 may include multiple transmitters. The receiver 208 includes electronics configured to receive wireless signals. In some situations, the receiver 208 may include multiple receivers. The receiver 208 and transmitter 206 receive and transmit signals, respectively, through an antenna 210. The antenna 210 may include separate transmit and receive antennas. In some circumstances, the antenna 210 may include multiple transmit and receive antennas.

The transmitter 206 and receiver 208 in the example of FIG. 2 perform radio frequency (RF) processing including modulation and demodulation. The receiver 208, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 206 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the base station functions. The required components may depend on the particular functionality required by the base station.

The transmitter 206 includes a modulator (not shown), and the receiver 208 includes a demodulator (not shown). The modulator modulates the signals to be transmitted as part of the downlink signals and can apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signals received at the base station 200 in accordance with one of a plurality of modulation orders.

The base station 200 includes a communication interface 212 for transmitting and receiving messages with other base stations. The communication interface 212 may be connected to a backhaul or network enabling communication with other base stations. In some situations, the link between base stations may include at least some wireless portions. The communication interface 212, therefore, may include wireless communication functionality and may utilize some of the components of the transmitter 206 and/or receiver 208.

FIG. 3 is a block diagram of an example of a UE device 300 suitable for use as each of the UE devices 101-104. In some examples, the UE device 300 is any wireless communication device such as a mobile phone, a transceiver modem, a personal digital assistant (PDA), a tablet, or a smartphone. In other examples, the UE device 300 is a machine type communication (MTC) communication device or Internet-of-Things (IOT) device. The UE device 300, therefore is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to UE device 300 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices.

The UE device 300 includes at least a controller 302, a transmitter 304 and a receiver 306. The controller 302 includes any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of a communication device. An example of a suitable controller 302 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 304 includes electronics configured to transmit wireless signals. In some situations, the transmitter 304 may include multiple transmitters. The receiver 306 includes electronics configured to receive wireless signals. In some situations, the receiver 306 may include multiple receivers. The receiver 304 and transmitter 306 receive and transmit signals, respectively, through antenna 308. The antenna 308 may include separate transmit and receive antennas. In some circumstances, the antenna 308 may include multiple transmit and receive antennas.

The transmitter 304 and receiver 306 in the example of FIG. 3 perform radio frequency (RF) processing including modulation and demodulation. The receiver 304, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 306 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the communication device functions. The required components may depend on the particular functionality required by the communication device.

The transmitter 306 includes a modulator (not shown), and the receiver 304 includes a demodulator (not shown). The modulator can apply any one of a plurality of modulation orders to modulate the signals to be transmitted as part of the uplink signals. The demodulator demodulates the downlink signals in accordance with one of a plurality of modulation orders.

FIG. 4 is a message flow diagram 400 for an example where a transmitting UE device 101 provides a location unavailable configuration 116 to a receiving UE device 102.

At transmission 402, the transmitting UE device 101 sends a location unavailable configuration message to the receiving UE device 102. Transmission 402, therefore, is an example of the location unavailable configuration transmission 116 discussed with reference to FIG. 1 . The location unavailable configuration message provides the configuration information to the receiving UE device to configure the receiving UE device 102 for HARQ messages for distance-based HARQ when location information is unavailable to the receiving UE device 102. Accordingly, the configuration indicates whether the receiving UE device transmits a HARQ message for data transmitted with a distance-based HARQ when the receiving UE device 102 does not know its location. For the example, the location unavailable configuration message is a Medium Access Control (MAC) Control Element (CE) in the Sidelink Control Channel (SCCH) transmitted in a groupcast transmission. In some cases, the location unavailable configuration message may be a PC5-S (upper layer message) delivered in the SCCH. Furthermore, the location unavailable configuration message may be transmitted as a 1-bit indicator in the SCI. Other techniques can be used to transmit the location unavailable configuration.

At event 404, a groupcast transmission is transmitted from the transmitting UE device 101 to the receiving UE devices of the group. At transmission 406, the transmitting UE device 101 sends a distance-based HARQ configuration to the receiving UE device 102 to configure the receiving UE device for distance-based HARQ. At transmission 408, a groupcast transmission is sent by the transmitting UE device to the members of the group. The groupcast transmission includes data and the associated SCI. For the examples herein, the distance-based HARQ configuration is sent in the header of a groupcast data transmission. More specifically, the HARQ configuration is sent in the SCI of the groupcast transmission. As discussed above, the SCI is encoded with more robust modulation coding scheme (MCS) than the data so that the receiving UE devices will receive this portion of the signal with a much greater success rate. The traffic portion of the packet might be encoded with a lesser robust MCS to ensure higher data throughput. Accordingly, for the examples herein, transmission 406 and transmission 408 are part of the same transmission at event 404. The two transmissions 406, 408 are shown as separate arrows in the figures to illustrate that the SCI can be successfully received while the data may not be successfully received in some situations. For the examples, the SCI portion of transmission 406 is successfully received and the data of transmission 408 is not successfully received by the receiving UE device 102. In some situations, information related to the HARQ configuration is transmitted over multiple channels. For example, in at least one revision of the NR V2X communication specification, the SCI is sent in two stages where a first part is carried by the physical channel PSCCH and the second part is carried in PSSCH. As specified in Rel-16, one of the fields in the first stage SCI in PSCCH indicates which 2nd-stage SCI (format A or B) is used and a second stage SCI is in the PSSCH indicates either format-2A for HARQ ACK/NACK and format-2B for NACK-only. The zone ID and communication range requirement is sent in the 2B. Accordingly, the transmitting UE device could implicitly request the receiving UE device to send a distance-based HARQ by indicating the groupcast type in the SCI.

At event 410, the receiving UE device 102 determines data in the transmission 408 was not successfully received. After successfully receiving the SCI portion of the groupcast transmission, the receiving UE device 102 unsuccessfully attempts to receive the data portion.

At event 412, the receiving UE device 102 determines that location information is unavailable. For example, the receiving UE device 102 may determine that GPS service is unavailable where GPS provides the information required for the UE device to determine UE device location. In some situations, the location determination is performed at a location server at the base station with assistance from the UE device. If the UE device determines that the base station cannot provide the location information where this technique is used, the receiving UE device determines that location information is unavailable.

At event 414, the receiving UE device applies the location unavailable configuration previously received from the transmitting UE device 101 to determine if a HARQ message should be sent. If it is determined that the HARQ message should be sent, a HARQ message is sent at transmission 416. Otherwise, no HARQ message is sent. The arrow representing the HARQ message is shown with a dashed line in FIG. 4 to indicate that the message is not sent where the configuration does not include HARQ feedback messages for distance-based HARQ when location information is unavailable.

FIG. 5 is a flow chart of an example of a method 500 of managing groupcast feedback based on location information availability. For the example, the method is performed by a UE device operating in a NR V2X system such as the system 100 described above. Accordingly, the method may be performed by the second UE device (receiving UE device) 102 when part of a group of the first UE device (transmitting UE device) 101.

At step 501, a location unavailable configuration message is received from the transmitting UE device. As discussed above, the location unavailable configuration message provides the configuration information to the receiving UE device to configure the receiving UE device 102 for HARQ messages for distance-based HARQ when location information is unavailable to the receiving UE device 102. Accordingly, the configuration indicates whether the receiving UE device transmits a HARQ message for data transmitted with a distance-based HARQ when the receiving UE device 102 does not know its location. For the example, the location unavailable configuration message is a Medium Access Control (MAC) Control Element (CE) in the Sidelink Control Channel (SCCH) transmitted in a groupcast transmission. In some cases, the location unavailable configuration message may be a PC5-S (upper layer message) delivered in the SCCH. Furthermore, the location unavailable configuration message may be transmitted as a 1-bit indicator in the SCI. Other techniques can be used to transmit the location unavailable configuration.

At step 502, a groupcast data transmission with distance-based HARQ configuration is received. For the example, at least the SCI portion is successfully received. The data portion may not be successfully received at step 502.

At step 504, it is determined whether the data portion of the groupcast data transmission is successfully received. In accordance with known techniques, the receiving UE device 102 evaluates the information in the transmission to determine if the data has been successfully received. If the data is successfully received, the method returns to step 502 for reception of the next transmission. Otherwise, the method proceeds to step 506.

At step 506, it is determined whether location information is available. If the location of the receiving UE device 102 is known or can be determined, the method continues at step 508. Otherwise, the method proceeds to step 510.

At step 508, it is determined whether the receiving UE device 102 is within the distance range for sending HARQ feedback. The distance based on the criteria specified by the transmitting UE device is calculated and evaluated to determine if HARQ feedback is required. If the receiving UE device is not within the distance range, the method returns to step 502 to receive the next transmission without sending HARQ feedback. Otherwise, the HARQ feedback is transmitted at step 512. As discussed above, distance-based HARQ feedback includes only NACK for the example. Accordingly, the receiving UE device 102 sends a NACK indicating that the data in the groupcast transmission was not successfully received before returning to step 502.

At step 510, the receiving UE device determines whether the location unavailable configuration requires transmission of HARQ feedback when location is not available. If HARQ feedback is required by the configuration, the method proceeds to step 512 where a HARQ message is transmitted. Otherwise, the method continues at step 514 where the receiving UE device refrains from sending HARQ feedback. For the example, the method returns to step 502 where a new groupcast message is received. In some situations, the method returns to step 501 to receive a new location unavailable configuration before receiving the next groupcast message at step 502.

FIG. 6 is a flow chart of an example of a method 600 of managing groupcast feedback based on location information availability. For the example, the method is performed by a UE device operating in a NR V2X system such as the system 100 described above. Accordingly, the method may be performed by the first UE device (transmitting UE device) 101 when transmitting groupcast transmission to a group of UE devices including the second UE device (receiving UE device) 102.

At step 602, it is determined whether distance-based HARQ will be used for groupcast messages. The transmitting UE device evaluates factors such as the QoS, number of UE devices in the group, and the available PSFCH resources. If it is determined that distance-based HARQ feedback should be used, the method continues at step 604. Otherwise, the method proceeds to step 606 where groupcast data is transmitted in a groupcast transmission with a groupcast HARQ not based on distance configuration.

At step 604, the location unavailable configuration is determined. For the example, the transmitting UE device 101 evaluates factors such as the QoS, number of UE devices in the group, and the available PSFCH resources to determine whether a receiving UE device should transmit HARQ messages when location information is unavailable. In some situations, the determination on whether HARQ feedback should be used by a receiving UE device that does not have location information is at least partially performed by a base station or the network. Accordingly, the transmitting UE device 101 may provide information to the serving base station and receive instructions on whether HARQ feedback should be used when location information is unavailable. Also, the base station may provide criteria or information that assists the transmitting UE device in determining the location unavailable configuration.

At step 608, the location unavailable configuration is transmitted to the receiving UE devices. As discussed above, the location unavailable configuration message provides the configuration information to the receiving UE devices to configure the receiving UE devices for HARQ messages for distance-based HARQ when location information is unavailable to the receiving UE device 102. Accordingly, the configuration indicates whether the receiving UE device transmits a HARQ message for data transmitted with a distance-based HARQ when the receiving UE device 102 does not know its location. For the example, the location unavailable configuration message is a Medium Access Control (MAC) Control Element (CE) in the Sidelink Control Channel (SCCH) transmitted in a groupcast transmission. In some cases, the location unavailable configuration message may be a PC5-S (upper layer message) delivered in the SCCH. Furthermore, the location unavailable configuration message may be transmitted as a 1-bit indicator in the SCI. Other techniques can be used to transmit the location unavailable configuration.

At step 610, a groupcast data transmission with distance-based HARQ configuration is transmitted to a group of UE device including the second UE device (receiving UE device 102. The groupcast data transmission includes distance-based HARQ feedback configuration.

At step 612, it is determined whether the groupcast transmissions to the UE devices should continue use distance-based HARQ or if the HARQ feedback should be switched to HARQ feedback that is not based on distance. The transmitting UE device evaluates factors such as the QoS, number of UE devices in the group, and the available PSFCH resources. If it is determined that distance-based HARQ feedback should continue to be used, the method continues at step 614. Otherwise, the method proceeds to step 606 where the next groupcast transmission uses HARQ feedback that is not based on distance.

At step 614, it is determined whether a new location unavailable configuration should be used for groupcast transmissions using distance-based HARQ. The transmitting UE device 101 evaluates factors such the QoS required for the receiving UE device, available resources and the number of UE devices in the group to determine if the configuration should be changed from the previous transmission. If no change in configuration is required, the method returns to step 610 where the transmitting UE device 101 transmits the next groupcast transmission. If configuration is change is required, the method returns to step 604 where the new configuration is determined. For the example of FIG. 6 , therefore, a new location unavailable configuration is transmitted only where the configuration has changed from the previous transmission. In some situations, however, the location unavailable configuration is transmitted with each groupcast transmission. Other techniques may also be used.

Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents. 

1. A method performed at a receiving user equipment (UE) device, the method comprising: receiving a location unavailable configuration from a transmitting UE device, the location unavailable configuration indicating whether hybrid automatic repeat request (HARQ) feedback should be provided for groupcast transmissions comprising a distance-based HARQ feedback configuration when location information is unavailable; determining a data portion of a groupcast data transmission from a transmitting UE device was not successfully received, the groupcast data transmission comprising a distance-based HARQ feedback configuration; determining that location information is unavailable; determining whether the location unavailable configuration requires transmission of a HARQ feedback message; transmitting the HARQ feedback message if the location unavailable configuration requires transmission of the HARQ feedback message; and refraining from transmitting the HARQ feedback message if the location unavailable configuration does not require transmission of the HARQ feedback message.
 2. The method of claim 1, wherein receiving the location unavailable configuration comprises receiving a control signal.
 3. The method of claim 2, wherein receiving the location unavailable configuration comprises receiving a Sidelink Control Channel (SCCH) signal in a groupcast transmission.
 4. The method of claim 3, wherein receiving the location unavailable configuration comprises receiving a Medium Access Control (MAC) Control Element (CE) in the SCCH channel.
 5. The method of claim 4, wherein the SCCH signal is transmitted in accordance with at least one revision least one revision of a Third Generation Partnership Project (3GPP) New Radio (NR) V2X communication specification.
 6. A receiving user equipment (UE) device comprising: A method performed at a receiving user equipment (UE) device, the method comprising: a receiver configured to receiving a location unavailable configuration from a transmitting UE device, the location unavailable configuration indicating whether hybrid automatic repeat request (HARQ) feedback should be provided for groupcast transmissions comprising a distance-based HARQ feedback configuration when location information is unavailable; a controller configured to determine: that a data portion of a groupcast data transmission from a transmitting UE device was not successfully received, the groupcast data transmission comprising a distance-based HARQ feedback configuration; that location information is unavailable; whether the location unavailable configuration requires transmission of a HARQ feedback message; and a transmitter configured to transmit the HARQ feedback message if the location unavailable configuration requires transmission of the HARQ feedback message and configured to refrain from transmitting the HARQ feedback message if the location unavailable configuration does not require transmission of the HARQ feedback message.
 7. The receiving UE device of claim 6, wherein the location unavailable configuration is transmitted in a control signal.
 8. The receiving UE device of claim 7, wherein the control signal is a Sidelink Control Channel (SCCH) signal in a groupcast transmission.
 9. The receiving UE device of claim 8, wherein the location unavailable configuration is transmitted as a Medium Access Control (MAC) Control Element (CE) in the SCCH channel signal.
 10. The receiving UE device of claim 9, wherein SCCH channel signal is transmitted in accordance with at least one revision least one revision of a Third Generation Partnership Project (3GPP) New Radio (NR) V2X communication specification.
 11. A method comprising: determining a location unavailable configuration for a receiving user equipment (UE) device, the location unavailable configuration determining whether the receiving UE device transmits a HARQ message in response to a groupcast transmission using a distance-based hybrid automatic repeat request (HARQ) feedback configuration when location information is unavailable to the receiving UE device; and transmitting the location unavailable configuration from a transmitting UE device to the receiving UE device.
 12. The method of claim 9, wherein the determining is performed by the transmitting UE device.
 13. The method of claim 9, wherein the determining is performed by a base station serving the transmitting UE device.
 14. The method of claim 9, wherein the determining is performed by a network serving the transmitting UE device and the receiving UE device.
 15. The method of claim 9, wherein the determining is performed by a combination of at least two of: the transmitting UE device, a base station serving the transmitting UE device; and a network serving the transmitting UE device and the receiving UE device.
 16. The method of claim 9, wherein the determining comprises evaluating at least one of: a quality of service (QoS) of communications with the receiving UE device, a number of UE devices in a group receiving the groupcast transmission, and available Physical Sidelink Feedback Channel (PSFCH) resources.
 17. The method of claim 9, wherein transmitting the location unavailable configuration comprises transmitting a Medium Access Control (MAC) Control Element (CE) in a Sidelink Control Channel (SCCH) signal in a groupcast transmission.
 18. The method of claim 15, wherein the RRC signal is transmitted in accordance with at least one revision least one revision of a Third Generation Partnership Project (3GPP) New Radio (NR) V2X communication specification.
 19. A transmitting user equipment (UE) device comprising: a controller configured to determine a location unavailable configuration for a receiving user equipment (UE) device, the location unavailable configuration determining whether the receiving UE device transmits a HARQ message in response to a groupcast transmission using a distance-based hybrid automatic repeat request (HARQ) feedback configuration when location information is unavailable to the receiving UE device; and a transmitter configured to transmit the location unavailable configuration to the receiving UE device.
 20. The transmitting UE device of claim 17, wherein the controller is configured to determine the location unavailable configuration at partially based on information received from a base station serving the transmitting UE device.
 21. The transmitting UE device of claim 17, wherein the controller is configured to determine the location unavailable configuration at partially based on at least one of: a quality of service (QoS) of communications with the receiving UE device, a number of UE devices in a group receiving the groupcast transmission, and available Physical Sidelink Feedback Channel (PSFCH) resources.
 22. The transmitting UE device of claim 17, wherein the transmitter is configured to transmit the location unavailable configuration by transmitting a Medium Access Control (MAC) Control Element (CE) in a Sidelink Control Channel (SCCH) signal in a groupcast transmission, the CE indicative of the location unavailable configuration.
 23. The transmitting UE device of claim 20, wherein the SCCH signal is transmitted in accordance with at least one revision least one revision of a Third Generation Partnership Project (3GPP) New Radio (NR) V2X communication specification. 